Reduced phosphomolybdate as photoassisted electrochemical crystalline sensor for trace Cr(VI) detection

Abstract

The development of a sensitive and efficient detection technology for trace toxic hexavalent chromium (Cr(VI)) in water is a pressing concern. In this study, an hourglass-type phosphomolybdate-based metal-organic network with the formula [Na 0.5 Cu 5.5 (H 2 O) 2 (btmbp) 4 ] [Mn(H 2 O) 3 ] 2 {Mn[H 6 P 4 Mo 6 O 31 ] 2 }•10H 2 O (1, btmbp = 4,4'-bis((1H-1,2,4-triazol-1-yl)methyl)biphenyl) was hydrothermally synthesized. The crystal network consists of a ladder-like two-dimensional layered structure constructed by vertical connections of onedimensional (1D) [Na 0.5 Cu 5.5 (H 2 O) 2 (btmbp) 4 ] 6+ metal-organic chains and 1D inorganic polyanionic chains. Compound 1 exhibits excellent electrochemical property and a wide light absorption range including visible light to accelerate the electron transfer in redox processes. When serving as a photoassisted electrochemical (PAEC) sensor for trace Cr(VI) detection, compound 1 exhibits a high sensitivity of 330.5 μA•μM −1 and a low detection limit of 0.95 nM (98.79 ppt) along with high anti-interference ability and excellent PAEC detection stability, outperforming most reported polyoxometalate-based sensors and equaling noble-metal sensors, far satisfying World Health Organization standards for Cr(VI) concentration in drinking water. This work provides a new photoelectrochemical sensor material for monitoring environmental pollutants.